The invention discloses an assembling device and method for tee pipes. The assembling device for the tee pipes comprises a controller, a pipe mechanical arm, a pipe assembling position, a first assembling mechanism, a second assembling mechanism and a third assembling mechanism, wherein the first assembling mechanism, the second assembling mechanism and the third assembling mechanism are arranged around the pipe assembling position. The pipe mechanical arm, the first assembling mechanism, the second assembling mechanism and the third assembling mechanism are electrically connected with the controller. The tee pipe assembling method includes the following steps that the pipe mechanical arm grabs the tee pipes and conveys the tee pipes to the assembling position. Nuts and pipe sleeves are put in the first assembling mechanism, the second assembling mechanism and the third assembling mechanism so that the nuts, the pipe sleeves and the axes of corresponding joints can be located on the same straight line. The nuts and the pipe sleeves are screwed into the three joints of the three tee pipes through the first assembling mechanism, the second assembling mechanism and the third assembling mechanism to complete assembling of the tee pipes. According to the assembling device and method for the tee pipes, the tee pipes are automatically assembled, and the assembling time is effectively shortened.